I'd like to understand a couple of things better than I do regarding MOSFETs. A lot of my projects use a MOSFET as a switching device driven from the output of a microcontroller, so the MOSFET would be logic level.
A resistor is ideal between the uC and the Gate of the MOSFET to limit current out of the uC. In calculating a value for this resistor, I believe the formula for doing that is Vcc @ 5V, Vgs, and uC pin current @20mA max... so 5V - Vgs = (5V-Vgs)/0.02 = Resistance.
This brings 2 question to mind for me, which may seem like simple questions but I need clarification regardless. As an example, I'm using this datasheet.
Figure 3 shows typical transfer characteristics. Using the 25°C plot line, my drain current is about 150mA. Does this mean that it takes about 2.2V into the gate for the MOSFET to switch on? Also, I hear the term "saturation" a lot. Is saturation considered the point where the MOSFET starts to conduct from Drain to Source, which if the above is correct would be when the gate reaches 2.2V? Maybe I'm way off on this.
I'm not the best at picking information out of datasheets. I'd like to have a better understanding of what voltage into the gate starts conduction from Drain to Source, and also how to determine what current into the gate from the uC pin is required, which I believe is called HFE. I believe HFE is determined by how much the load current into the Drain is, but perhaps I'm mistaken?
Thanks.
A resistor is ideal between the uC and the Gate of the MOSFET to limit current out of the uC. In calculating a value for this resistor, I believe the formula for doing that is Vcc @ 5V, Vgs, and uC pin current @20mA max... so 5V - Vgs = (5V-Vgs)/0.02 = Resistance.
This brings 2 question to mind for me, which may seem like simple questions but I need clarification regardless. As an example, I'm using this datasheet.
Figure 3 shows typical transfer characteristics. Using the 25°C plot line, my drain current is about 150mA. Does this mean that it takes about 2.2V into the gate for the MOSFET to switch on? Also, I hear the term "saturation" a lot. Is saturation considered the point where the MOSFET starts to conduct from Drain to Source, which if the above is correct would be when the gate reaches 2.2V? Maybe I'm way off on this.
I'm not the best at picking information out of datasheets. I'd like to have a better understanding of what voltage into the gate starts conduction from Drain to Source, and also how to determine what current into the gate from the uC pin is required, which I believe is called HFE. I believe HFE is determined by how much the load current into the Drain is, but perhaps I'm mistaken?
Thanks.